Diopters, Prisms, Focus screens - getting the best view for accurate focusing

One of the reasons I initially started shooting with the Rolleiflex was for the wonderful viewfinders with are big and bright.   Each Rolleiflex platform has several viewfinder options: on the 6000 series there are 5 finders, on the Hy6 there are four different finders, and 3 for the TLR's.    I like to be in control of the camera as much as possible, and personally rarely use the autofocus features.  When I do use AF, I find that it affects my compositional framing since I tend to center to the subject more.   

Besides the finder choices, another great thing about the Rolleiflex is that DHW-fototechnik offers lots of corrective diopters for their prisms and WLF pop up magnifiers, and they are not too expensive.  (I'm going to list a table of the different corrective diopters very soon.)

My problem is that my eyesight isn't that great and I have an astigmatism too.  That means even with the correct diopter in place, I still can't see really sharp images in the finder without glasses.  I won't bore you all with the effort I went into with building my own custom magnifying finders or experimentation with numerous focusing screens right now (maybe in a later post), but instead will get right to the solution for those of you who have an astigmatism but want to shoot without your glasses.  It's the Televue Dioptrx.   This is a corrective eyepiece for astronomers to fit to their telescopes, but amazingly its about the right size to fit on the 45 degree prism eyecups and also the same diameter of the 3x lupe finders.  Note - I have no affiliation with TeleVue at all.  I am just very happy these exist.  If you know your prescription, you can just select the closest one - they come in .25 diopter increments.  If you are in between, go to the higher value. 

I bought mine from OPT Telescopes but you can get them several places.  Here's a link to their page with the dioptrx.    

These come with a rubber eyecup and have a screw on mount cap that fits over the Rollei 45 degree prism eyecup. You can just remove the rear piece and slip it over the rollei eyecup and then screw in the dioptrx and then as you tighten look through and rotate it such that the angle is correct for your astigmatism (you'll see it get sharp - a little off and things tilt at an angle - way off its blurry).  It will stay on really pretty well.  If you get wild with your Hy6 and hop around like I do, you might want a bit more security.  I ended up gluing a large stainless steel washer on the back of the rear dioptrx cap that had a slightly smaller hole in it and this holds my dioptrx on very well.  I actually have two of these.  The second one is for my lupe finder.  It looks a bit funky but since they are the same diameter - I just use a piece of the blue masking tape around the seam to hold them together.